1. Technical Field
The present invention relates generally to a method for making extruded, pellet products with minimal tempering time prior to puffing. More particularly, the invention manipulates extrusion settings to produce a half-product that requires minimal drying and/or moisture equilibration prior to expansion by heating.
2. Description of Related Art
Pellet, or xe2x80x9chalf productxe2x80x9d technology, is known in the snack industry for producing puffed snack products. Pellet products, prior to puffing (expansion), provide several advantages, which include the following: a high bulk density, which makes them less expensive to ship, breakage resistance during shipment, and the ability to form intricate shapes. Once puffed pellet products have a light, expanded texture because of their low product density and a thin product wall thickness, for example less than 0.20 inches.
Generally, an expandable pellet is one that increases in volume by upwards of 100% from the rapid vaporization of water within the pellet during rapid heating of the pellet. Consequently, the density of the pellet decreases. For example, the initial density of a typical pellet piece is greater than about 40 lb/ft3 and following expansion is reduced down to a final density of less than about 25 lb/ft3.
Typical pellets require processing to produce a finished snack product. In a first step, the ingredients, which generally include cereal products and starches, are hydrated to form an extrudable mixture for forming pellets. The extrudable mixture is subsequently gelatinized to create dough that is subsequently passed through a die where after the extruded mixture is cut into pellets. After formation, the unfinished pellets, which contain from about 20% to about 30% moisture by weight, are processed through a dryer to arrive at a final moisture of about 9% to about 18% for either storage or later processing after moisture equilibration.
To produce a product that has desirable texture, density and other characteristics, the pellets made using the prior art method need to be dried and moisture equilibrated, which is essentially a curing stage. This curing stage can extend from a period of less than an hour up to several days or longer. This step reduces the moisture content significantly from about 25% down to about 12% for example. Once dried, the pellets can then be expanded by heating with, for example, frying, baking (hot air impingement), or microwave heating. This drying/curing stage adds expense and time to the pellet manufacturing process.
Processes for producing pellets for use as a snack food product are known in the art. For example, U.S. Pat. No. 3,348,950 to Weiss describes a process for making snack food product by first mixing together corn, sucrose, water, and flavoring. This mixture is combined with a second mixture of yellow corn grits, water, and sodium bicarbonate. The combined mixture is pre-cooked under pressure of 14 psi to 20 psi and temperatures between 247xc2x0 F. and 259xc2x0 F. The gelatinized dough is shaped, and then dried and/or moisture equilibrated before puffing using deep-fat frying. This process requires extensive drying time and a tempering period of xc2xd to 2 hours.
Animal protein is known to be used for forming pellets. U.S. Pat. No. 4,163,804 to Meyer et al. describes producing expandable pellets by extruding animal parts at temperatures between 250xc2x0 F. and 330xc2x0 F. with an extrusion pressure over 500 psig. It is essential to this process that the raw material be animal parts that have a high average undenatured protein (collagen) content. The high collagen content allows the formation, under the disclosed process conditions to be formed after extrusion into a shaped sustaining form and cut into puffable pellets. It is disclosed that stretching ratios of from 2:1 to 5:1 are used in some applications of this invention but stretching is not used when annular shapes are made. No disclosure is made of required SME, die opening size, or stretching ratio as a means of eliminating the tempering step.
U.S. Pat. No. 4,262,028 to Meyer et al. includes adding starch to ground animal parts. Starch contents of up to 75% are disclosed, but the extrudate mixture still requires a high average collagen content of 25% of animal parts to form a thermoplastic moldable mass. Meyer discloses that the addition of starch makes it possible to obtain puffing of the product as it exits from the extruder. Meyer further states that this treatment can eliminate the need for additional drying of the product prior to any additional puffing in a fryer. However, such a product would no longer posses the beneficial pellet properties of high bulk density and resistance to breakage when shipping. Meyer does not disclose using any post-extrusion stretching to compress the prepuffed extrudate to densities and thicknesses in accordance with pellets.
U.S. Pat. No. 5,132,127 to Wisdom discloses a process for making a pellet product by combining a high moisture material with one or more low moisture farinaceous ingredients followed by extrusion. The extrudate in Wisdom is partially stretched by gravity at less than a 2:1 ratio over a several hour drying step that is required prior to frying or hot air puffing.
U.S. Pat. No. 6,165,530 to Mathew et al. and U.S. Pat. Nos. 6,224,933 and 6,242,034 to Bhaskar et al. describe processes to make pellets which involves using tension rolls to stretch a ribbon extruded from the die face. These stretching steps however are performed at less than a 2:1 ratio. Therefore, pellets manufactured by these processes still require a drying step prior to expansion.
Therefore, a method is needed for producing an extruded pellet without a drying/curing stage while maintaining desirable pellet density and expansion characteristics. Further, it is desired to have a pellet product that is less expensive and time consuming to manufacture than conventional pellet methods and does not require animal parts as an ingredient.
The present invention is an improved method for producing starch-based, or other farinaceous-based pellets that after expansion have a light, expanded texture. The expansion of the pellets made from with this method do not require a prior dehydration/tempering step. The primary raw material of the pellets is a farinaceous starch mixture with no animal parts or collagen sources required. This includes yellow corn meal, white corn meal, corn masa flour, rice meal, wheat flour, oat flour, and/or mixtures thereof. Other ingredients can include sucrose, dextrose, dry molasses, wheat bran, modified food starches, leavening, shortening, vegetable protein, and emulsifier. These ingredients are added by weight to a blender for dry mixing. Thereafter, this mixture is fed to an extruder along with water and/or steam for hydration.
During extrusion, the mixture is mechanically sheared and gelatinized within the extruder under conditions of shear, pressure, and temperature to form an extrudate. Upon passing through a die, the extrudate forms a ribbon, which xe2x80x9cprepuffsxe2x80x9d upon exiting the extruder due to steam being released from the reduction in pressure. This prepuffing facilitates a reduction in the moisture content of the ribbon from about 15% to about 30% down to about 9% to about 20%.
To convert the prepuffed ribbon to an unpuffed pellet consistency, the ribbon is stretched by passing it through, for example, a series of rollers. The tension in the ribbon, provided by the stretching rollers, counteracts the expansion caused by the prepuffing at the die due to steam formation. This results in the ribbon, after initially expanding, to return to an unexpanded, thin pellet like nature with a density greater than about 40 lb/ft3 and a thickness of less than about 0.10 inches.
Particularly with the stretching, the stretching rollers have a rotational velocity that exceeds the ribbon""s linear velocity. The rollers apply a light pressure sufficient to grab the ribbon causing it to stretch without substantially creating a calendering effect. The stretched ribbon""s velocity is thereby increased to at least two times (2:1) or more, preferably at least three times (3:1) or more, the velocity it had when it exited the extruder. The stretched ribbon is then cut by a roll cutter or alternative cutting device into preform chip pieces, i.e., pellets, for subsequent expansion (puffing) by heating with frying, hot-air popping, or microwaving.
After puffing, the finished product has a volume significantly greater, such as twice, that of the pellet""s volume and a density significantly lower, such as at least one half, that of the pellet""s density. Also, the finished product has another benefit of shape retention of the die insert""s orifice. The finished product has a light, expanded, and appetizing texture that is characteristic of expanded, pellet products. Further, the finished product can be made without the need for a time consuming pellet dehydrating and/or conditioning stage prior to expansion.
The above as well as additional features and advantages of the present invention will become apparent in the following written detailed description.